127 lines
4.6 KiB
C++
127 lines
4.6 KiB
C++
/**
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* @file VelocityConstraint.h
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* @brief Constraint enforcing the relationship between pose and velocity
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* @author Alex Cunningham
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*/
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#pragma once
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#include <gtsam/base/numericalDerivative.h>
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#include <gtsam/nonlinear/NonlinearFactor.h>
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#include <gtsam_unstable/dynamics/PoseRTV.h>
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#include <boost/bind/bind.hpp>
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namespace gtsam {
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namespace dynamics {
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/** controls which model to use for numerical integration to use for constraints */
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typedef enum {
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TRAPEZOIDAL, // Constant acceleration
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EULER_START, // Constant velocity, using starting velocity
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EULER_END // Constant velocity, using ending velocity
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} IntegrationMode;
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}
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/**
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* Constraint to enforce dynamics between the velocities and poses, using
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* a prediction based on a numerical integration flag.
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*
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* NOTE: this approximation is insufficient for large timesteps, but is accurate
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* if timesteps are small.
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*/
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class VelocityConstraint : public gtsam::NoiseModelFactorN<PoseRTV,PoseRTV> {
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public:
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typedef gtsam::NoiseModelFactorN<PoseRTV,PoseRTV> Base;
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protected:
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double dt_; /// time difference between frames in seconds
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dynamics::IntegrationMode integration_mode_; ///< Numerical integration control
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public:
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/**
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* Creates a constraint relating the given variables with fully constrained noise model
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*/
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VelocityConstraint(Key key1, Key key2, const dynamics::IntegrationMode& mode,
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double dt, double mu = 1000)
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: Base(noiseModel::Constrained::All(3, mu), key1, key2), dt_(dt), integration_mode_(mode) {}
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/**
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* Creates a constraint relating the given variables with fully constrained noise model
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* Uses the default Trapezoidal integrator
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*/
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VelocityConstraint(Key key1, Key key2, double dt, double mu = 1000)
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: Base(noiseModel::Constrained::All(3, mu), key1, key2),
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dt_(dt), integration_mode_(dynamics::TRAPEZOIDAL) {}
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/**
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* Creates a constraint relating the given variables with arbitrary noise model
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*/
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VelocityConstraint(Key key1, Key key2, const dynamics::IntegrationMode& mode,
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double dt, const gtsam::SharedNoiseModel& model)
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: Base(model, key1, key2), dt_(dt), integration_mode_(mode) {}
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/**
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* Creates a constraint relating the given variables with arbitrary noise model
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* Uses the default Trapezoidal integrator
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*/
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VelocityConstraint(Key key1, Key key2, double dt, const gtsam::SharedNoiseModel& model)
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: Base(model, key1, key2), dt_(dt), integration_mode_(dynamics::TRAPEZOIDAL) {}
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~VelocityConstraint() override {}
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/// @return a deep copy of this factor
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gtsam::NonlinearFactor::shared_ptr clone() const override {
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return boost::static_pointer_cast<gtsam::NonlinearFactor>(
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gtsam::NonlinearFactor::shared_ptr(new VelocityConstraint(*this))); }
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/**
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* Calculates the error for trapezoidal model given
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*/
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gtsam::Vector evaluateError(const PoseRTV& x1, const PoseRTV& x2,
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boost::optional<gtsam::Matrix&> H1=boost::none,
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boost::optional<gtsam::Matrix&> H2=boost::none) const override {
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if (H1) *H1 = gtsam::numericalDerivative21<gtsam::Vector,PoseRTV,PoseRTV>(
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std::bind(VelocityConstraint::evaluateError_, std::placeholders::_1,
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std::placeholders::_2, dt_, integration_mode_), x1, x2, 1e-5);
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if (H2) *H2 = gtsam::numericalDerivative22<gtsam::Vector,PoseRTV,PoseRTV>(
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std::bind(VelocityConstraint::evaluateError_, std::placeholders::_1,
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std::placeholders::_2, dt_, integration_mode_), x1, x2, 1e-5);
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return evaluateError_(x1, x2, dt_, integration_mode_);
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}
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void print(const std::string& s = "", const gtsam::KeyFormatter& formatter = gtsam::DefaultKeyFormatter) const override {
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std::string a = "VelocityConstraint: " + s;
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Base::print(a, formatter);
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switch(integration_mode_) {
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case dynamics::TRAPEZOIDAL: std::cout << "Integration: Trapezoidal\n"; break;
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case dynamics::EULER_START: std::cout << "Integration: Euler (start)\n"; break;
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case dynamics::EULER_END: std::cout << "Integration: Euler (end)\n"; break;
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default: std::cout << "Integration: Unknown\n" << std::endl; break;
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}
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std::cout << "dt: " << dt_ << std::endl;
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}
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private:
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static gtsam::Vector evaluateError_(const PoseRTV& x1, const PoseRTV& x2,
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double dt, const dynamics::IntegrationMode& mode) {
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const Velocity3& v1 = x1.v(), v2 = x2.v();
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const Point3& p1 = x1.t(), p2 = x2.t();
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Point3 hx(0,0,0);
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switch(mode) {
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case dynamics::TRAPEZOIDAL: hx = p1 + Point3((v1 + v2) * dt *0.5); break;
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case dynamics::EULER_START: hx = p1 + Point3(v1 * dt); break;
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case dynamics::EULER_END : hx = p1 + Point3(v2 * dt); break;
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default: assert(false); break;
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}
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return p2 - hx;
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}
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};
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} // \namespace gtsam
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